linux-kernel - [PATCH] blkdev: use an efficient way to check merge flags

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Date:	Wed,  2 Apr 2014 23:19:06 +0800
From:	Jianyu Zhan <nasa4836@...il.com>
To:	axboe@...nel.dk
Cc:	hch@....de, jack@...e.cz, viro@...iv.linux.org.uk,
	kmo@...erainc.com, namjae.jeon@...sung.com, nasa4836@...il.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH] blkdev: use an efficient way to check merge flags

A bitwise flag comparison could be done using a more efficient bit-ops way.

Signed-off-by: Jianyu Zhan <nasa4836@...il.com>
---
 include/linux/blkdev.h | 13 +++----------
 1 file changed, 3 insertions(+), 10 deletions(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1e1fa3f..adfa40a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -655,16 +655,9 @@ static inline bool rq_mergeable(struct request *rq)
 static inline bool blk_check_merge_flags(unsigned int flags1,
 					 unsigned int flags2)
 {
-	if ((flags1 & REQ_DISCARD) != (flags2 & REQ_DISCARD))
-		return false;
-
-	if ((flags1 & REQ_SECURE) != (flags2 & REQ_SECURE))
-		return false;
-
-	if ((flags1 & REQ_WRITE_SAME) != (flags2 & REQ_WRITE_SAME))
-		return false;
-
-	return true;
+	return (flags1 & (REQ_DISCARD | REQ_SECURE | REQ_WRITE_SAME)) ^
+	       (flags2 & (REQ_DISCARD | REQ_SECURE | REQ_WRITE_SAME))
+		== 0;
 }
 
 static inline bool blk_write_same_mergeable(struct bio *a, struct bio *b)
-- 
1.9.0.GIT

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